Sunlight and Health

A certain amount of sunlight on your skin may be necessary for good health. Sunlight activates a gene called pom-C, which in turn helps create melanin that determines skin color and enhances sex drive, the endorphins or "happiness hormones", and leptin, which helps burn fat to keep you thin. In the USA, people who have high sunlight exposure (farmers, mail carriers) live the longest. The key is to find methods to receive adequate sunlight exposure while reducing skin damage.

Why Do People Suntan?

The most common reason given for suntanning is that time in the sun brings a psychological feeling, often intense, of well being and relaxation. The physical warmth of the suns rays is also very pleasant. After becoming more tan, most people feel better about themselves. These are deep psychological feelings and seem to be part of our genetic response to sunlight.

What is Suntanning and is it Dangerous?

An estimated 22 million Americans tan in salon sun beds each year and a much larger number tan outside every year. Suntanning slowly produces pigment (melanin) in the skin as ultraviolet rays in sunlight penetrate the skin. The buildup of melanin helps to blocks ultraviolet rays and also serves as a powerful anti-oxidant. Additional, sunlight produces a redness or erythema that when combined with melanin results in the esthetically preferred skin color tone.

People suntan for a variety of reasons - to enhance physical beauty and sexual attractiveness, for mood elevation. and to counter depression. Some use sunlight to improve skin health as with psoriatic lesions.

But is light suntanning healthy or dangerous?

Consider the following:

Humans evolved in the presence of abundant sunlight. Geneticists and archeologists calculate that humans lost their body hair 1.2 million years ago but only started wearing clothes 72,000 years ago. So for about 1,128,000 years our ancestors frolicked nude in the Garden of Eden and thrived.

USA cancer rates are highest in the northern states with the least sunshine.

Multiple sclerosis is much lower in areas with more sunlight exposure.

But my doctor says sunlight is dangerous!

Despite the medical establishment's near unanimity (with the exception of many cancer research scientists) on the issue of sunlight exposure, serious health errors have been promoted to the public in the past.

In 1927, 12,745 physicians endorsed smoking Lucky Strike cigarettes as a healthful activity. In the 1940s and 1950s, thousands of prominent surgeons were used in national cigarette advertisements to reassure the public about the safety of cigarette smoking.

In the 1950s, lobotomies were promoted for mental disorders and produced near-totally dysfunctional people.

In the 1960s and 1970s, diets high in omega-6 polyunsaturated fats and partially hydrogenated fatty acids such as safflower oil and margarine were recommended to reduce heart disease. However, long term studies found that, while such diets decreased heart disease, they increased the total death rate and the cancer rate and produced accelerated aging.

For the past 30 years, cosmetic companies and a small group of very vocal, publicity-seeking dermatologists have strongly advocated that chemical sunscreens should be heavily applied before any exposure to sunlight. They insisted that such sunscreen use would prevent skin cancer and protect your health. This was in spite of a dearth of adequate safety testing of these chemicals. (It should be emphasized that most dermatologists are much more cautious and careful)

While it is established that excessive sun exposure will produce serious skin damage, it is also possible that we need some minimum amount of sunlight to maintain good health and a positive mental state. Sitting in a dark room for years did not help the brilliant industrialist and movie producer, Howard Hughes. Sunlight produces vitamin D in the skin (and probably other unknown molecules) and also strongly affects pineal gland function - considered one the the master glands controlling body function.

Questions or Advice?

How Much Sunlight is Needed?

Studies have found that 20 to 30 minutes per day supplies the required amount of vitamin D. On the other hand, persons afflicted with depression from SAD (seasonal affective disorder) often need several hours of full spectrum lighting to alleviate depression.

Cholecalciferol: the Sunlight "Vitamin"

Most of the body's cholecalciferol or vitamin D3 (commonly known as vitamin D) supply, about 75%, is generated by the skin's exposure to UVB rays. Anthropologists have postulated that the development of light skinned people reflected a need for vitamin D. Humans probably arose in tropical climates since the temperature at which we are neither cold nor hot is about 70°F. As humans moved to colder and darker climates, the weaker sunlight favored reproduction of less-pigmented persons who could produce vitamin D in their skin with less light.

Most of the body's cholecalciferol or vitamin D3 (commonly known as vitamin D) supply, about 75%, is generated by the skin's exposure to UVB rays. Anthropologists have postulated that the development of light skinned people reflected a need for vitamin D. Humans probably arose in tropical climates since the temperature at which we are neither cold nor hot is about 70°F. As humans moved to colder and darker climates, the weaker sunlight favored reproduction of less-pigmented persons who could produce vitamin D in their skin with less light.

Using a sunscreen drastically lowers the cutaneous production of vitamin D3. A low blood level of vitamin D is known to increase the risk for the development of breast and colon cancer and may also accelerate the growth of melanoma. Recent news coverage has highlighted the problems of Vitamin D deficiency, especially amongst African Americans.

Cholecalciferol itself is not biologically active. It must be hydroxylated twice for activation, the first time in the liver and the second in the kidney (in the proximal convoluted tubule). The final product 1,25-dihydroxycholecalciferol or 1,25(OH)2D is secreted into the blood for delivery to target cells, where it acts the same way as steroid hormones do: it binds to a receptor protein in the cell's nucleus, which then binds to regulatory sequences on DNA. This complex induces the transcription of RNA, which codes for proteins involved in cell function.

The primary function of vitamin D is whole-body calcium homeostasis. Along with parathyroid hormone and calcitonin, vitamin D provides the control mechanism for preventing hypocalcemia or hypercalcemia. One of the most important proteins induced by vitamin D is a calcium-binding protein in the duodenal mucosa. This protein increases calcium absorption in response to low calcium supply or increased physiologic requirements (such as growth or lactation). Vitamin D is also involved in the handling of calcium by the kidney. Thus, vitamin D is technically a steroid hormone synthesized in the kidney in response to calcium needs. There is a specific 1,25(OH)2D receptor protein found in most nucleated cells in the body. This implies that vitamin D has more functions than just calcium homeostasis (which would only require receptors in gut, bone, and kidney tissues). Vitamin D may be involved in immune function and skeletal muscle activity and may suppress cell proliferation.